Method and Device for Processing Uplink Signal in WLAN System

1. A method for processing, by an access point (AP), uplink (UL) signals in a wireless local area network (WLAN) system, the method comprising: receiving a request to send (RTS) frame from a first station (STA) among a plurality of STAs; transmitting an UL spacetime division multiple access (SDMA) control frame to the first STA, wherein the UL SDMA control frame includes a second group identifier (ID) of a second group to which a second STA that will be allowed to perform UL multi-user (MU) multiple-input multiple-output (MIMO) transmission belongs, among first group IDs of first groups to which the first STA belongs; transmitting a group ID management frame to the first STA and the second STA, wherein the group ID management frame indicates locations of spatial streams to be used by the first STA and the second STA in the second group, wherein the group ID management frame includes a membership field for each of the first groups and a preamble sequence field for each of the first groups; receiving a first UL signal from the first STA and a second UL signal from the second STA, wherein the first UL signal and the second UL signal are transmitted simultaneously by using a constant amplitude zero auto-correlation (CAZAC) sequence which is used as a training sequence, wherein different training sequences are used for the first UL signal and the second UL signal; and processing the first UL signal and the second UL signal.

2. The method of claim 1 , further comprising: transmitting a number of spatial streams used by the first STA and the second STA when the first STA and the second STA perform the UL MU-MIMO transmission.

3. The method of claim 1 , wherein the membership field for each group indicates whether or not the first STA belongs to each of the first groups and whether or not the second STA belongs to each of the first groups.

4. The method of claim 1 , wherein the preamble sequence field indicates an index of a preamble sequence used by the first STA and the second STA when the first STA and the second STA perform the UL MU-MIMO transmission.

5. The method of claim 4 , wherein the index of the preamble sequence is predetermined in a codebook formed between the AP and STAs.

6. An access point (AP) for processing uplink (UL) signals in a wireless local area network (WLAN) system, the AP comprising: a radio frequency (RF) unit for transmitting or receiving a radio signal; and a processor connected to the RF unit, and configured to: receive a request to send (RTS) frame from a first station (STA) among a plurality of STAs; transmit an UL spacetime division multiple access (SDMA) control frame to the first STA, wherein the UL SDMA control frame includes a second group identifier (ID) of a second group to which a second STA that will be allowed to perform UL multi-user (MU) multiple-input multiple-output (MIMO) transmission belongs, among first group IDs of first groups to which the first STA belongs; transmit a group ID management frame to the first STA and the second STA, wherein the group ID management frame indicates locations of spatial streams to be used by the first STA and the second STA in the second group, wherein the group ID management frame includes a membership field for each of the first groups and a preamble sequence field for each of the first groups; receive a first UL signal from the first STA and a second UL signal from the second STA, wherein the first UL signal and the second UL signal are transmitted simultaneously by using a constant amplitude zero auto-correlation (CAZAC) sequence which is used as a training sequence, wherein different training sequences are used for the first UL signal and the second UL signal; and process the first UL signal and the second UL signal.

7. The AP of claim 6 , wherein the processor is further configured to: transmit a number of spatial streams used by the first STA and the second STA when the first STA and the second STA perform the UL MU-MIMO transmission.

8. The AP of claim 6 , wherein the membership field indicates whether or not the first STA belongs to each of the first groups and whether or not the second STA belongs to each of the first groups, and wherein the preamble sequence field indicates an index of a preamble sequence used by the first STA and the second STA when the first STA and the second STA perform the UL MU-MIMO transmission.

9. The AP of claim 8 , wherein the index of the preamble sequence is predetermined in a codebook formed between the AP and STAs.

10. The method of claim 1 , wherein the RTS is received only from the first STA, and wherein UL SDMA control frame is transmitted to the first STA based on the received RTS.

11. The AP of claim 6 , wherein the RTS is received only from the first STA, and wherein UL SDMA control frame is transmitted to the first STA based on the received RTS.